There is known a coupling that transmits torque applied to an input shaft to an output shaft. For example, a coupling for an electric power steering is placed between an input shaft connected to an electric motor and an output shaft connected to a steering wheel, to transmit output torque of the electric motor to the steering wheel.
The below-mentioned Patent Literature 1 discloses a coupling comprising: a first hub (connection base), which is fitted to an end of an input shaft connected to an electric motor or the like; a second hub (connection base), which is fitted to an end of an output shaft connected to a steering wheel or the like; and a spacer (rotation transmitter), which is placed between the first and second hubs. The first and second hubs are connected with each other via the spacer, so that torque is transmitted from the input shaft to the output shaft. Here, as the spacer, is used an insert-molded part obtained by uniting a first rotation transmitting member of metal or hard resin, and a second rotation transmitting member of rubber elastic body to cover the first rotation transmitting member.